Specializes in med/surg, telemetry, IV therapy, mgmt.
which rationale describes why the cusp valves are different from the valves at the pulmonary artery and aorta? select all that apply.
a- chordi tendoni are needed to prevent back flow of blood into the atria due to the level of pressure occurring during ventricular contraction
b- cusp valves prevent back flow of blood by closing after "forward" pressure reduces during diastole
c- valves are needed to keep blood flowing from low pressure to high pressure vessels attached to the heart
d- valves are different because of the kind of blood that passes through their openings
in this case a valve is a flap that is being used to control the flow of blood into and out of the heart. their job is to keep the blood flowing in one direction--forward. the heart beat is always pushing the blood forward, so each valve is closing to prevent too much blood from entering the next chamber or vessel beyond what it is able to physically accommodate. in closing they also prevent back flow of the blood when there are momentary pauses in the pressure of the heart's pumping action. the chordi tendoni are extremely strong, tough cords that ensure that the cusp valves snap close tightly to prevent any backflow since the pressure is much higher during ventricular systole.
why do veins have valves when arteries don't? select all that apply
a- because blood flow accelerates in the venous system
b- because blood flow slows in the venous system
c- to prevent back flow of blood as venous walls don't have smooth muscle like arteries
d- to prevent blood clots from developing in the lower extremities
blood flow does not slow in the venous system. if it did, blood would back up and become congested in the peripheral veins. veins have less elastic and muscular tissue than arteries. the valves within them are merely to prevent back flow of blood during the short pauses between diastole and systole.
which is the best explanation of why fetal heart rate is 120-160 beats per minute?
a- the smaller the mammal, the faster the heart beat
b- the fetus exists in a reduced oxygen level in the uterus, so the heart rate increases to meet oxygen demand
c- the conduction system of the heart is immature; therefore it is more prone to a faster rate than an adult
d- because the fetus doesn't "breathe" in the uterus, its heart rate stabilizes to circulate blood
there is a physical principle at work here:
cardiac output
heart rate - beats per minute
stroke volume - amount of blood pumped per beat
high heart rate x small amount of blood per pump = the cardiac output
Daytonite, BSN, RN
1 Article; 14,604 Posts
which rationale describes why the cusp valves are different from the valves at the pulmonary artery and aorta? select all that apply.
why do veins have valves when arteries don't? select all that apply
which is the best explanation of why fetal heart rate is 120-160 beats per minute?